New information: Hackett
et al.'s (2008) comprehensive analysis set new standards for sampling in terms
of genes for comparative analysis of the Aves: 19 independent loci and 32 kb of
nDNA sequences. Their study targeted resolving the deep branches in the avian tree;
resolution among these branches has largely been intractable in previous
analyses. Their results confirmed a lack of relationship of the cathartids to
the Ciconiiformes (thus supporting our proposal 241)
and generally support the traditional relationship of the cathartids to the
Accipitriformes (Falconiformes here considered separate - that will be the
subject of another proposal). However, the bootstrap support for that
relationship is only 61%, below their 70% threshold. Although odds are still good
that they will eventually fall out as sisters, technically the current data
cannot confirm that the Accipitriformes are monophyletic if Cathartidae is
included; in fact, collapsing nodes with less than 70& support the nodes
collapse to a polytomy that would include a number of orders, including even
the Passeriformes.

Discussion: NACC has
already moved Cathartidae back to Falconiformes (sensu lato) and I will do a
proposal to follow this if the current one is rejected. I propose that we treat
the Cathartidae in their own order, Cathartiformes, as is the case in much
paleontological literature. The rationale for this is two-fold: (1) the support
for monophyly of the Accipitriformes is weak if Cathartidae is included, and
(2) regardless of whether they are shown to be sisters, the Cathartidae deserve
the rank of order, in my opinion, because they are diagnosable as a
monophyletic group in the fossil record as far back as many or most taxa ranked
as orders. If we were to combine orders anytime we found sister relationships,
we'd eventually end up with one giant order, so there has to be an independent
criterion. Rather than make this something having to do with tradition or some
eclectic concept of degree of morphological distinctiveness, I suggest that we
use a rough proxy for "time as independent unit", namely how far back
in fossil record one can diagnose individuals as belonging to the group. Using
the criterion as "mid Eocene or earlier" actually works pretty well
for modern nonpasserines. Certainly, the paleo people are comfortable with
ranking them as an order. With all appropriate caveats, a Google search today
on "Cathartiformes" gets 3400 hits, so we're not using a novel
classification.

Recommendation: YES, for
elevating Cathartidae to rank of order, to recognize that the group is as old
as most orders of modern birds and to acknowledge lingering lack of strong
support as the sister group to Accipitriformes. Of minor note is that this
proposal would also remove a family from Incertae Sedis status.

Comments from Stiles: YES. I
agree that a time-based criterion for ordinal rank is at least as instructive
as one based on "pure" morphology, especially now that we are aware
of a number of morphological "odd bedfellows" (albeit not necessarily
in the same order) like flamingos and grebes! Cathartiformes certainly
qualifies here, and I do not favor placing the Cathartidae in Falconiformes
especially since this weakens support for the latter as a monophyletic
group."

Comments from Zimmer:
"YES. This approach makes the most sense to me (for reasons already stated
by Van and Gary), especially given the date of the split, and the weakened
support for monophyly if we put them back in with Falconiformes."

Comments from Robbins:
"Before accepting the "mid-Eocene or earlier" criterion, I'd
appreciate the opinions from avian paleo experts, such as Dave Steadman. In
addition, given the understandably contentious nature surrounding avian fossil
identifications, I had questions about the claim that cathartids have been
identified from the Eocene. I consulted with Univ. of Kansas vertebrate
paleontologist Larry Martin about the Eocene cathartid skeleton and he stated
that if it is based on the Eocathartes
described by Wetmore, that specimen has been reidentified as a non-cathartid.
Thus, it behooves us to confirm that there is indeed a cathartid from the
Eocene before voting on this proposal."

Comments from Schulenberg:
"NO. We probably should have a fuller discussion of the issue of "support
for monophyly of the Accipitriformes is weak if Cathartidae is included."
The study with the most data, Hackett et al., seem to lean towards a
sister-clade relationship between Cathartidae and accipitriform raptors,
although there are scant details in their paper. (I don't know when or if that
team will get around to publishing on this question in more detail, but we can
always hope. In the meantime, Hackett et al. have unanalyzed data on 10,000
more base pairs, and 30 more taxa - this work is ongoing.)

"Beyond that, I have
reservations about relying so heavily on "paleontologists." There
aren't that many paleontologists who work on ancient birds, and I'm not sure if
I trust them. It wasn't that long ago that major figures in the field (Feduccia,
Olson) were claiming some strange phylogenetic relationships, such as that half
or more of all birds could be traced back to Charadriiformes, or that ducks,
flamingos, and one (!) genus of avocets were related. Perhaps there's a
difference between accurately identifying the fossilized tip of a tibiotarsus
to an order, and inferring phylogenetic relationships based on a small mound of
fossilized tips of tibiotarsi, but I need to be convinced that the difference
is great enough to overcome my distrust of the entire field.

"All this is not to say that
I know a bird order when I see one, only that I'm not sure that we want to put
this question in the hands of "paleontologists."

Additional comments from Remsen:
"Cathartid presence in Eocene is based on Diatropornis
Milne-Edwards, 1892 (fide Paleobiology online data-base + confirming comment on
that diagnosis from Emslie at same site, and a Cracraft paper in Condor
on evolution of cathartids in Old World). You can all Google your way to the
official citations, etc."

Comments from Jaramillo:
"YES - Higher level taxon changes are always problematic, partially
because it is quite a subjective matter. One person's order is another person's
family etc. To me Cathartidae are rather unique, and at most they appear to be
only distantly related to the Accipitriformes. The fact that they have bounced
around between Ciconiiformes and Falconiformes is telling, this group does not
fit neatly anywhere. My reading of the data is that they will come out to be
sisters with the Accipitriformes; nevertheless they are an old lineage. I think
it is a good resolution to give them their own order, and if data ever comes
out to challenge this, then we can change then."

Comments from Cadena:
"YES, albeit hesitantly. The Hackett et al. (2008) analyses show that
Cathartidae and Accipitridae are sister taxa. Although support for this result
is not great, it is consistent with the long-term status quo in which these two
lineages are included in the same order, Falconiformes. Thus, in retrospect,
perhaps the wisest thing would have been to leave Cathartidae in the
Falconiformes and not place it incertae sedis. Now that this move has been made
(and I realize I voted yes on that proposal) and the Cathartidae are unplaced,
I guess recognizing Cathartiformes is OK, particularly considering that this
rank has been applied to these birds in the past. Leaving Tom's valid comments
on paleontology aside, I sympathize with Van's argument about the age of the
vulture lineage. However, I don't think lineage age is a sufficient reason to
make taxonomic changes; adopting this as a standard would require changing
ranks for a whole bunch of clades, and is not strictly necessary to maintain a
classification that is consistent with phylogeny. But well, that's a more
general discussion that we might want to have at some other time. I would
personally favor not changing higher-level classification unless they are
obvious problems of non-monophyly."